Solids often contain residual amounts of amine. For example, waste solids from processes using amine solvents to extract organic products from reaction streams, solids formed as by-products in the production of triethylamine or other amines, and solids produced in amine-solvent de-oiling processes may contain residual amounts of amine.
In addition to the solids identified above, solids containing residual amounts of amines are produced in processes for dewatering sludges or breaking oil-water emulsions which contain solid matter. For example, a process for dewatering sludges containing solid matter and water using an amine or amine mixture having an inverse critical solution temperature is described in U.S. Pat. No. 3,899,419 to Emanuel, incorporated herein by reference. Improvements on the Emanuel process are disclosed in U.S. Pat. No. 3,925,201 to Ames, U.S. Pat. No. 4,056,466 to Peters, and U.S. Pat. No. 4,830,754 to Nowak et al., each of which are incorporated herein by reference.
In Emanuel, U.S. Pat. No. 3,899,419, a sludge is mixed with an amine or mixture of amines having an inverse critical solution temperature with water. At a temperature below the inverse critical solution temperature of the amine, the water will dissolve in the amine. The solid matter in the sludge can then be removed to leave a more or less single-phase mixture. Increasing the temperature of the singe-phase mixture above the inverse critical temperature of the amine results in the formation of a two-phase system: a water component containing residual amine, and an amine component containing residual water. These two phases can then be separated, thus achieving the desired dewatering of the sludge. The solid matter removed in such a process may subsequently be dried to yield a dried solids material. This material, however, contains a residual amount of amine due to the extraction technique.
Ames, U.S. Pat. No. 3,925,201, discloses a method for minimizing the residual amine in both the solid matter and in the water component by adding an alkaline composition to the sludge before addition of the amine. In practice, however, the addition of the alkaline composition to the sludge before the addition of amine leads to increased viscosity of the sludge, making mixing and pumping of the sludge difficult. This problem was addressed in U.S. Pat. No. 4,830,754 to Nowak et al., incorporated herein by reference. In Nowak et al., U.S. Pat. No. 4,830,754, an alkaline composition is added to the sludge coincident with the step of mixing the sludge with the amine in an amount sufficient to remove substantially all of residual amine from the solid matter.
A related technique is disclosed in U.S. Pat. No. 4,002,562 to Ames et al., incorporated herein by reference, wherein a method for breaking emulsions containing oil, water and solid matter is taught. According to the process of Ames et al., U.S. Pat. No. 4,002,562, an amine or mixture of amines having an inverse critical solution temperature with water is added to the emulsion at a temperature below the inverse critical solution temperature. Any solid matter present in the emulsion can then be separated by a variety of known techniques such as centrifugation or filtration. After separation of the solid matter, the remaining mixture is a more or less homogeneous mixture of water, oil and amine. When the temperature of the water-oil-amine mixture is then raised above the inverse critical solution temperature of the amine, two phases are produced: a water phase containing a small amount of amine, and an oil-amine phase containing a small amount of water. These phases may then be separated to achieve separation of the original emulsion. The solid matter removed in such a process may subsequently be dried to yield a dried solids material which contains a residual amount of amine.
Dried solids of the types discussed above contain residual amounts of amine in varying quantities. Such residual amine, however, is undesirable because of environmental concerns associated with the disposal of such solids in, for example, landfills. In addition, due to the relatively strong odor of many amines, residual amine content in solids has been found undesirably noxious.
Accordingly, there is a need in the art for a method of reducing the residual amine contained in solid matter. In addition, there is a need in the art to reduce the residual amine content in the dried solids produced by the processes for dewatering sludges or breaking oil-water emulsions containing solid matter using an amine having an inverse critical solution temperature with water.